The field of the disclosure relates generally to a turbine engine, and more particularly, to turbine bucket diagnostics, including the usage of a passive wireless sensing system that may be used in diagnostic applications for a gas turbine engine.
Known gas turbine engines typically include a compressor and a turbine, each with a series of alternating stator buckets (i.e., blades, members) and rotor buckets. During operation of a gas turbine engine, turbine buckets are exposed to and become highly stressed under harsh environmental conditions, such as extreme temperatures, high velocity working fluids, high velocity air flow, high rotational velocities and vibrations. Given these conditions, it is important for turbine rotor bucket health to be monitored closely. Generally, bucket failures may be prevented through proper monitoring of strain levels and crack formation in highly stressed areas on the bucket and through the collection of sufficiently precise and accurate bucket data (e.g., temperature, strain, vibration, or any other mechanical parameters).
Conventional bucket monitoring systems may measure the temperature at the inlet and outlet of both the compressor and the turbine, and some known systems measure the temperature of internal components of the gas turbine engine. Some known systems include a thermocouple sensor to measure temperature of the internal components. However, known thermocouple sensors only gather data from discrete points inside the gas turbine engine, which may not provide enough data for an adequate thermal analysis of the gas turbine engine. Alternatively, some known systems employ infrared cameras to measure temperature of the internal components from locations external to the gas turbine engine through a borescope. However, these known systems also limit the amount of data that can be gathered about the internal components. Other known systems employ fiber optic sensors to measure temperature. However, known fiber optics do not provide sufficient resolution to consistently measure temperature of the internal components. To measure vibration, for example, tip timing is a conventional method that measures bucket vibration frequency. Generally, the presence of a crack alters the operating vibration frequency of a bucket and indicates that a bucket is compromised. However, results from this method have proved unreliable in many applications. Another more expensive and time consuming conventional method to determine cracks includes shutting down the turbine engine and visually inspecting the buckets. This type of inspection, though, provides no information about the stress occurring during operation, is prone to unreliability, and is very expensive because of both the required labor and the need to shut down the engine. Moreover, many conventional monitoring systems begin to fail during exceedingly fast rotating applications (e.g., greater than 5000 RPM).